(1) Field of the Invention
This invention is concerned with a method of loading rivets and in particular it is concerned with a method of loading a column of hollow rivets for use in pull-through-blind-riveting on to a long-stemmed headed mandrel.
(2) Prior Art
In one kind of well-known blind-riveting system (that is to say, a fastening system whereby a hollow rivet can be set in aligned holes in superposed parts of a workpiece from one side only of the workpiece), a column of 30 to 60 rivets, may, depending on their length, be assembled with the rivets head-to-tail on a mandrel which, at the tail end of the foremost rivet, there is a setting head. The mandrel is inserted in a blind-riveting tool which has means for gripping the mandrel at its rearward end and moving it back and forth, a split nosepiece which can abut the head of the foremost rivet and hold it against the accessible face of the workpiece while the mandrel is pulled through the rivet to set it, and means for urging the rivets forward after each setting stroke so as to project the foremost one through the nosepiece and up to the mandrel head ready for the next riveting operation. This kind of blind-riveting system will be referred to hereinafter as "pull-through blind-riveting".
A mandrel for use in pull-through blind-riveting has to be of high quality to ensure that it is strong enough not to break while yet it is thin enough to be accommodated in the bores of the rivets, and is therefore an expensive item which requires its repeat use over and over again rather than dispense with it after setting one column of rivets. Accordingly, it is necessary to load it with a fresh column of rivets when one has been used up.
U.S. Pat. Nos. 4,338,714 granted July 13, 1982 and 4,346,804, granted Aug. 31, 1982 describe a method and an apparatus of loading hollow rivets on to a headed mandrel so that they can be set in a pull-through blind-riveting operation where the method as described is preferably carried out by threading the mandrel right through a sleeve on which there is a column of hollow rivets assembled head-to-tail and transferring the rivets to the mandrel while withdrawing the sleeve. This method although a great improvement over previous methods requires the mandrel to be thin enough to be threaded through the sleeve; this results in a weaker mandrel than may be desirable, since strength is an important necessity for such mandrels, and in the rivets not being held centrally on the mandrel. Other disadvantages of this method lie in the fact that the wall of the sleeve has to be thin and made to very close tolerances; such sleeves may not be readily available in inexpensive materials.
It is an object of the present invention to provide an improved method of loading hollow rivets on to a headed mandrel which method avoids the above-mentioned disadvantages.